Conimbriga (prov. Lusitania, current municipality of Condeixa-a-Nova, District of Coimbra, Portugal) is a Roman city of indigenous roots known since the sixteenth century, the subject of excavations and various publications since 1890 and, since 1930, the place of systematic archaeological excavations that have exposed the site and saved it as a major Roman site in the Iberian Peninsula. A method for calculating the population number of a Roman town is presented, based on the study of the domestic architecture of the c. 20% of excavated area. The method allows to go beyond the mere number of inhabitants and to suggest some reconstruction of the structure of the population. Conclusion point to a small town (c. 5500 inhabitants) and a deeply stratified structure, with almost a third of slaves and dependents and a small decurionate class, not exceeding c. 7% (around 40 families). Keywords-Roman population; municipal elites; domestic architecture 1. introduction Among various research projects on Conimbriga, a recent one can be mentioned, which dealt with the systematic study of the domestic architecture of the town, which although often referenced, particularly because of the preserved mosaics, had never been the subject of systematic treatment. This situation is paradoxical. The archeological research in Conimbriga began with the domestic architecture. This is a feature that Conimbriga shares with towns such as Pompeii, Herculaneum and Ostia, but not with many other archaeological sites in the orb of the Roman empire. The first four moments of city research, namely, the small excavations triggered by an occasional finding, in 1873, the first major excavations of 1899, the excavation of the site by the Faculty of Letters in 1930 and the excavations from 1929 to 1944 by the DGEMN, exposed, all of them-temporarily the first two, definitely the others-domestic architectural fragments, and none of them, public monuments of significance 2. The Late Empire city-wall, a public monument of substance, has never been subject to thorough research, 1 Trabalho desenvolvido no âmbito do projeto UID/ELT/00196/2013, financiado pela FCT-Fundação para a Ciência e a Tecnologia.